Transducer



Dec. 25, 1945. A S HOWELL 2,391,627

TRANSDUGER 2 Sheets-Sheet l Filed Jan. 19, 1944 Dec. 25, 1945. A. s. HOWELL.

TRANSDUCER Filed Jan. 19, 1944 2 Sheets-Sheet 2 Fizz/@wwwa i El 'Ill

Patented Dec. 25, 1945 TRANSDUCER Arthur S. Howell, Rochester, N. Y., assiznor to Stromberg-Carlson Company, Rochester, N. Y., a corporation oi.' New York Application January 19, 1944, Serial No. 519,073

9 Claims.

This invention relates to an acoustical transform a lower pole piece, each of these parts havducer more commonly referred to as a soundpowered or self-energized telephone.

A telephone of this type is adapted toY serve f either as a transmitter or receiver thus when two of such, telephones have their respective terminals connected by suitable conductors in an electrical circuit, the' arrangement comprises a complete telephone system which operates without an external source of current or power other than the sound from the speakers voice. Such a soundpowered telephone is especially useful for military purposes and therefore it must be small in size so that it can be used in conjunction with a helmet and its construction must be such that it will not bedamaged when overloaded by loud blasts.

The main feature of the invention relates tov from the detailed description and claims when taken with the drawings in which:

Fig. 1 is a plan View ofthe telephone with the casing thereof removed;

Fig. 2 is a section through the telephone taken substantially on the line 2-2 of Fig. 7;

Fig. 3 is an exploded perspective view ofthe frame plate and one permanent magnet, a portion ofthe frame plate being broken away;

Fig. 4 is a perspective view of the upper pole member;

Fig. 5 is a perspective view of the supporting block on which the reed armature is mounted;

Fig. 6 is 'a perspective View` of the reed armature;

Fig. 'Z is a section through the telephone taken on line i-l of Fig. 1; Fig. 8 is a section through the telephone taken g on the line 8 8 of Fig. 2;

Fig. 9 is a section through the telephone taken substantially on the line 9-8 of Fig. l;

Fig. l0 is a perspective view of a terminal strip; and

Fig. l1 is a fragmentary showing of a transmitter mouth piece. v l

In the drawings, the numeral 5 designates a circular frame plate,'preferably made of mag` netic steel of high permeability. This frame has punched therefrom, a pair Vof parts 6 and 6a which are bent up in spaced parallel relation to ing its upper corners cut away so that it tapers to the pole faces l, la (Fig. 7). The frame has secured to its upper surface (Figs. 3 and 7), at each end of the parts 6, 6a of the pole piece, a rectangular permanent magnet 9, constituting a pair of magnets preferably made of Alnico V which serve as flux sources. These magnets are conveniently secured to the frame plate, in the parallel position shown, by means of an adhesive such as a phenolic resin.

The rectangular space (Fig. 2) between the magnets t, e on the one hand and parts S, 6a of the pole piece on the other, is just sufficient to receive the hollow flattened spool it, of insulating material on which there is wound a coii li, preferably of double enamel wire #39. It will be noted that the ends of the spool it, engage the pole parts t, @a respectively and that the pole faces t, la of these parts are substantially iush (Fig. 8) with the lower surface of the central opening through the spool. This opening through the spool is of such dimensions that a flexible reed-type armature l2 of magnetic material, can vibrate freely therein. One end of this armature is clamped as by a screw i3, in the recessed portion of a segment-shaped supporting block it while the other end of the armature projects beyond the pole piece for connection to a diaphragm i5 to be described. The block. if), which is made of nona-magnetic material, such as brass, is fastened by screws it, it (Fig. 9) to the frame plate with the recess in the block; communieating with the opening through the spool. It will thus be seen that the plate serves a triple purpose. It forms one pole piece, it also serves as the frame or base of the device and it further serves as a magnet Contact and as a magnetic connector between the magnets and the pole piece region of the frame.

The opposite pole member I8 (Fig. 4) is formed with pole parts it, isa in the same manner as the frame 5, except that only sufficient material is allowed outside of the pole piece region to provide for its suitable. mechanical mounting and to provide a suitable area of contact withthe magnets 9. This pole member is fastened by suitable. screws, to the upper 4surface of the supporting block it in contact with the upper surface of the magnets 9, 9 and with the pole faces 20 and 20a (Fig. 8) of the parts I9, l9a in spaced registry with pole faces 1 and la. It will be noted that the pole faces 20, 20a are substantially flush with the upper inside surface of the opening through spool Il. The pole member Il then fulillls a dual purpose since it provides one pole piece region and it serves as a magnetic contact and magnetic connector bel tween the magnets 8 and this region.

-The lower surface oi the frame plate 5 (Fig. 8) serves as a support for a circular corrugated diaphragm I5. This diaphragm, which has approximately the same diameter as the frame l,

' has its border clamped to the border of the frame with 'a thin washer 23 of non-magnetic material, such as aluminum, mounted between these clamped parts. The means for clamping the diaphragm to the frame comprises a circular cover 'in the frame to draw the mentioned parts together. The center of thel diaphragm lis connected to the free end of the reed armature I2 by a connecting rod 24 which passes through the opening in the frame 5 resulting from the upward forming of the part 6.' In the arrangement shown, the lower end of the connecting rod is secured to the diaphragm I5 while the upper iently established by means of the spacing washer 23 and said clearance will then be equal to the thickness of the spacing washer. If viscosity effects are neglected, the spacing may be reduced to a value only suiiicient to insure that the normal travel of the armature will not be unduly restricted by the diaphragm hitting the frame.

i considering the practical dimensional tolerances threaded portion of the rod passes through a hole in the free end o! the armature I2. 'I'he nuts 28 (Fig. 8) threaded on the rod, engage each surface at the armature to serve as a convenient fastening means which also functions to permit adjustment of the eilective length of the rod.

It is en important requirements: this device 5.

that it have the ability to withstand blasting` sound pressures, without damage. The corrugations in the thin diaphragm il are an aid in strengthening it. However, this is often insumycient and auxiliary means of protection must be provided. By reducing the clearance between the diaphragm I5 and the frame-5, the travel ot-the diaphragm in one direction is limited by the frame except for such small unsupported areas that result from necessary openings in the frame. 'I'he cavity or space between the diaphragm Il,

'and the trame I functionsacoustically as it it were not separated by the frame l, from the large mace about the armature and the pole cover plate 24, forms the entire eiiective acoustic v compliance in front of the diaphragm. Therefore, in order to obtain the maximum eilective `reductionintheeeparatioxrbetweenthesurfaces-o! the frame l and the cover-'plate 24 which denne the total diaphragm cavity. the diaphragmtoi'ramesepmtionisreducedeither start to appear or until the travel 'ofthe die'- 'phrlgmisundulyrestricted Thediaphragmto cover plate separation is then reduced imtil acoustic limitations partly involvingthesileand proximite of Il, become productiveotalnssinresponse. Byplacingthe cormgationsentirelyonthecoverplatesideot' theplaneottheborderotthedisphnsmthe trametodiaphregmcieerancemaybeconvenof the parts involved.

The response curve (not shown) of the unit described has a rst resonance peak at approximately 1350 cycles per second and a second resonance peak at approximately 2000 cycles per second. i

The iirst resonance peak is primarily deterlx mined by the constants of the moving diaphragmarmatum system and the stiffness of the total cavity behind the surface of the diaphragm adjacent the frame.

'I'he second resonance peak is largely determined by the size andnumber of the holes 2l in the cover plate 24 together with the cavity between the cover plate and the diaphragm I5.

It will be understood, however, that the resonant effects due to conditions at one side of the diaphragm tend to modify the resonant eilects due to conditions at the other side thereof.

On the upper surface of the frame l (Fig. 8), there is mounted a terminal segment or strip 28 of insulating material, having spaced upstanding lugs 28a. These lugs 28a serve as lateral supports for the metal contactors l, to which the I conductors II, li from the respective ends of the coll II, are soldered.

The parts mounted on the upper side of the frame (Fig. 2) are enclosed in a cup-like casing l33 or molded insulating material .having at its rim, a projecting Vxperipheral ilange 34. 'Ihis ilange is fastened to the border of cover plate 24 which projects Ibeyond the edge oi' the frame l. This casing has molded therein, metal inserts or jack contacts 35. These contacts which respectively engage the contactors I0, are adaptedto receive plug-contacts (not shown) in which the conductors of the telephone circuit (likewise not shown) terminate. It will be understood that the conductors'can be solderedv directly to the jack contacts 35 in which case, the terminal segment 28 and the contactors Il. mounted thereon, will be omitted.

When the device is to be usedas a receiver, an annular ear cap ll is adhesively fastened to the exposedsm'taceoithe coverplateasshownin Pig. 8. On the other hand, when the device is tobeusedasatransmittertheearcapwillbe replaced by a conventional mouthpiece Il (Fig.

wnatrclaim 1s:

l. In a transducer unit, a trame o f ferromagnetic material having spaced upstanding pole pieces struck up therefrom, a pair of permanent magnets of high coercive material contacting said frame in the region o i said pole pieces, a top plate `o! ferromagnetic material.. spaced pole pieces on said plate, means for mounting seid plate in fixed relation to said. frame to contact said magnets, with the free ends of the pole pieces thereon extending-toward the iree ends ol .the pole Vpieces on said frame, a coil mountedl between sus piste and said trame adjacent am 'pole pieces, creed o! ferromagnetic materiel j the last mentioned end portion of said reed whereby said unit can translate sound into electrical energy and vice versa.

Y region of said pole pieces, a top plate of ferro-v magnetic material having spaced pole pieces struck up therefrom, means Ifor mounting said plate in fixed relation to said frame to contact said magnets, with the free ends of the pole pieces thereon extending toward the free ends of the pole pieces on said frame, a hollow coil mounted between said plate and said frame with the open ends of said coil terminating adjacent said pole pieces, a reed of ferromagnetic material iixedly mounted at one end to extend through said coil and having its other end portion extending into the neld of innuence of said pole'pieces, and means including a diaphragm connected to the last mentioned end portion of said reed,

-whereby said unit can translate sound into elecsaid frame, a. pair-of permanent magnets of highA coercive material contacting said frame in the region of said pole pieces, a top plateof ferro= magnetic material, spaced pole pieces on said plate, means for mounting said plate in fixed relation to the front side of said frame to contact said magnets, with the free ends of said pole pieces thereon extending toward the free ends of pole pieces on said frame, a coil mounted between said plate and said frame adjacent said pole pieces, a reed of ferromagnetic material ilxedly mounted at one end and having its other end portion extending into the iield of influence of said pole pieces as wel-las of said coil, means including a diaphragm secured at one surface s l its margin to the reverse side of said frame and having its central portion connected to the last mentioned end portion 0f said reed whereby said unit can translate sound into electrical energy and vice versa, and a cover plate secured to the other marginal surface of the diaphragm "to provide a cavity, said cover plate having holes therein, said holes and said cavity serving to cause resonant eilects in the 'range of two thousand cycles.

4. In a transducer unit, a frame of ferromagsaid diaphragm, said cover platehaving several holes therethrough serving with said cavity to eiect a predetermined resonance peak in the frequency response oi' said unit.

5. In a transducer unit, a frame of ferromagnetic material, spaced upstanding pole pieces on said frame, a pair of permanent magnets of high coercive material contacting said frame in the region of said pole pieces, a top plate of ferromagnetic material, spaced pole pieces on saidplate, means for mounting said plate in fixed relation to said frame to contact said magnets,

said frame, a coil mounted between said plate,

and said frame, a reed of ferromagnetic material iixedly mounted at one end and having its other end portion extending into the field of iniluence of said pole pieces as well as of said coil, and means including a concentrically corrugated diaphragm secured at its margin to the reverse side of said frame and having its central portion connected to the last mentioned end portion of said reed whereby said unit can translate sound into electrical energy and vice versa, all of the corrugations in said diaphragm being positioned with respect to said frame beyond a plane deiined by the margin of said diaphragm whereby limited spacing isfpossible between the frame and the diaphragm.'

6. In a transducer unit, a frame of ferromagnetic material having spaced pole pieces struck up therefrom, a. top plate of ferromagnetic material secured in spaced 'relation to the front side of said frame and having spaced pole pieces struck therefrom to project in the direction of the free endsof said ilrst mentioned pole pieces, the spacing between the pole pieces on said plate being substantially equal `to the'spacing between the pole pieces on said frame.-l a pair of permanent magnets of high coercive material, secured to said frame and in contact with' said plate in a position where each magnet substantially spans the space between the pole pieces thereon, a. hollow coil positioned between said pole pieces with the v open ends of the coilpositioned adjacent said netic material, spaced upstanding polepieces on said frame, a pair of permanent magnets of high coercive material contacting said frame in the region of said pole pieces, a top plate 0f ferromagnetic material, spaced .pole pieces 0n said plate, means for mounting said plate in xed re. lation to the-front side' of said frame to contact said magnets, with the free ends of the polepieces thereon extending .toward the free ends of the pole -pieces onsaid frame, a coil mounted between said plate and said frame in the region of said pole pieces, a reed of ferromagnetic material iixedly mounted at one end and having its other end portion extending into the field of inuence of said pole pieces as well as of said coil, means including a concentrically corrugated diaphragm secured at one marginal surface tothe reverse side of said frame and having its central portion connected tothe last mentioned end p0rtion of said reed whereby said unit can translate sound into electrical energyand vice versa, and a cover plate secured to the other marginal surpole pieces, a reed of ferromagnetic material iixedly mounted at one end and having its other end portion projecting through said coil into the field of iniiuence of said pole pieces, and a di-v aphragm having its central portion connected to the proiecting end of said reed. g

'1. In a transducer unit, a frame of ferromagnetic material having spaced pole pieces struck up therefrom, a top plate of ferromagnetic material secured in spaced relation to the front side of said frame and having spaced pole pieces struck therefrom to project inthe direction of the free ends of said first mentioned pole pieces, the spacing between the pole pieces on said plate being substantially equal to the spacing between the pole pieces on said frame, a paix` of perma nent magnets of high coercive material, secured to ,said frame and in contact with said plate in a position where eachmagnet substantially spans the space between the pole pieces thereon, a hollow coil positioned between said pole pieces .with the open endsl of the coil positioned adjacent said pole pieces, a reed of ferromagnetic material ilxedly mounted at one end and having its other end portion projecting through said coil into the field of influence of said pole pieces and a ditace of the diaphragm and defining a cavity with'7s aphragm fixedly mounted by its margin at the reverse side of said frame and having its central portion connected to the projecting end of said reed a. 'In a transducer una. a frame of ferromag- 'netic material having spaced pole pieces struck uptherefrom, atop plate of ferromagnetic material secured in spaced relation to the front side of said frame and having spaced pole pieces the space between the pole pieces thereon, a hollow coil positioned between said pole pieces with the Open ends 0i the coil positioned adjacent said pole pieces, a reed of ferromagnetic material iixedly mounted at one end and having its other end portion projecting 'through saidcoil into the eld of influence of said pole pieces and a corrugated diaphragm mounted by its margin in -parallel spaced relation to the reverse side of said frame, said corrugations being located with 'respect to said frame beyond a plane deilned by the margin of said diaphragm, means connecting the central portion of said diaphragm and the projecting end of said reed and a perforated cover enclosing the side of said diaphragm remote from said frame thereby providing a cavity having an eilective acoustic compliance. j

9. In a transducer unit, a frame offerromagnetic material, spaced upstanding pole pieces on said frame, a pair of permanent magnets of highcoercive material contacting. said trame in the region of said pole pieces, a top plate of terromagnetic material, spaced pole pieces on said plate, means for mounting said plate in ilxed relation to said frame to contact said magnets, with the free ends oi' the pole pieces thereon extending toward the free ends oi the pole pieces on said frame, a coil mounted between said plate and said frame, a reed of ferromagnetic material ilxedly mounted at ope end and having its other end portion extending into the ileld ot iniiuence of said pole pieces as well as ofsaid coil, and means including a concentrically corrugated diaphragm `secured at its margin to the reverse side of said frame and having its central pOrtion connected to the last mentioned end portion of said reed whereby said unit can translate sound into electrical energy and vice versa, all of thel lcorrugations in said diaphragm being positioned at one sideot a plane deilned bythe margin oi said diaphragm.

ARTHUR S. HOWELL. 

